The most suitable energy storage technology but . . .

Current Scottish pumped storage capacity

Pumped storage is a well proven technology in use in Scotland and across the world. The Cruachan station on Loch Awe became fully operational in 1967 and was the first reversible pump storage hydro system to be built in the world. Cruachan generated 885 GWh of electricity in 2008

The Foyers hydro electric scheme was originally built by the british Aluminium Company in 1896 to power an aluminium smelter and was the first large-scale commercial hydro-electric scheme in the UK. It was redeveloped to focus on pumped-storage in 1969.

Diagram of Cruachan pumped storage hydro scheme

How does it work?

A pumped-storage hydroelectric power plant is a net consumer of energy but allows energy to be stored when electricity is plentiful and released for generation in times of high grid demand. Water is pumped uphill to a high reservoir when the demand, and price, for electricity is low. During hours of peak demand, when the price of electricity is high, the stored water is released through turbines to produce electric power.

Unlike most other types of power station hydroelectric power plants can be brought online almost immediately, making them eminently suitable for dealing instantly with quite large fluctuations in grid demand.

How much storage capacity do we need?

The storage capacity we will require depends on the capacity of renewables installed and the extent of upgrades to the transmission network,including any new interconnectors or the European ‘supergrid’. Assuming the Scottish government’s most ambitious scenario for renewables is realised then increased storage will be required. It is calculated that installing energy storage capacity of some 7 GW by 2030 would alleviate the constraints identified, with most of the constraints relieved with less than 10 hours of storage. Installing 3.5 GW of storage will alleviate 75% of constraints.

What new pumped storage is planned?

Two large-scale new pumped storage schemes are being planned for the Great Glen area of the central Highlands by power generation, distribution and supply company Scottish and Southern Energy (SSE). The plants, with a combined generation capacity of some 900MW, are planned for Coire Glas, north-west of Loch Lochy, and Balmacaan, near Invermoriston. They would be able to provide more than 1,000 gigawatt hours of electricity annually to help meet peak demands. With environmental impact investigations under way, SSE aim to submit planning applications this year.

It is also to submit to Scottish Ministers an application for consent to develop a 60MW pumped storage scheme at its existing Sloy hydro electric power station at Loch Lomond, allowing it to produce an additional 100GWh (gigawatt hours) of electricity in a typical year to help meet peak demand. In total the new schemes should increase Scotland’s pumped storage capacity by a little over 100%

Sites for any further pumped storage schemes are in scarce supply and likely to attract a lot of opposition from environmental groups. Proposals have been mooted for seawater pumped storage hydro and underground pumped storage schemes, but the costs could prove prohiiibitive. For the immediate future it looks as though pumped storage may only be able to meet between a third and a half of Scotland’s future energy storage needs.

Less than 1,000MW, that is for sure. However, that is not the point if pumped storage. Pumped storage is used to even out supply and demand. The electricity used to pump the water uphill is surplus to requirements, and would not be used for anything else. This makes it cheap. The water is then allowed to flow downhill through the turbines when there is greater demand and electricity is more expensive.

This is a very interesting article. What are the projected costs of the proposed facilities at Coire Glas and Balmacaan? What is the payback period and how do the economics work? What is the capacity of each individual project?